This invention relates to a method of authenticating the identity of a party involved in communicating over a computer network system using the intersection of password sets. As defined in this specification and the appended claims, a party includes a user, a resource, a computer program, and other entities capable of communicating over the network system.
In a computer network system in which users share network resources, the threat exists that unauthorized users may attempt to gain access to the network resources by posing as legitimate users. Additionally, unauthorized users might also create so-called "Trojan horse" programs that pose as legitimate system applications for the purpose of gaining confidential information from network users. Because of these threats, before parties can communicate securely on a network, they must be able to authenticate their identities to each other.
One of the traditional methods to prove a party's identity to another is to demonstrate the knowledge of a shared secret password. An unauthorized user does not know the secret password and, thus, cannot pose as an authorized party.
As networked systems becomes more complex, however, this simple scheme may not be sufficient. As shown in FIG. 1, for example, in some networked systems, different resources may be shared by different groups of users. In the example of FIG. 1, resource X is shared by the users in group A, resource Z is shared by the users in group B, and resource Y is shared by the users in both groups A and B. In this case, at least three secret passwords, Px, Py, and Pz, are necessary to accommodate the proper sharing of resource Y, without allowing the unauthorized sharing of resources X and Z.
Although this type of scheme works well in most cases, a drawback to this scheme is that if the password for resource Y of a user in group A becomes compromised, a new password for resource Y will have to be distributed to users in both groups A and B. Thus, all users will be inconvenienced by the security breach within a single group.
Accordingly, there exists a need for a method of authentication that provides flexibility in the sharing of resources, while at the same time provides convenience in password distribution.